Objectives:To measure the effect of social distancing on reducing daily deaths,infections and hospital resources needed for coronavirus disease 2019(COVID-19)patients during the first wave of the pandemic in Nordic co...Objectives:To measure the effect of social distancing on reducing daily deaths,infections and hospital resources needed for coronavirus disease 2019(COVID-19)patients during the first wave of the pandemic in Nordic countries.Methods:The observations of social distancing,daily deaths,infections along with the needed hospital resources for COVID-19 patient hospitalizations including the numbers of all hospital beds,beds needed in ICUs and infection wards,nursing staffs needed in ICUs and infection wards were collected from the Institute for Health Metrics and Evaluation(IHME)by the University of Washington.The observations of social distancing were based on the reduction in human contact relative to background levels for each location quantified by cell phone mobility data collected from IHME.The weighted data per 100,000 population gathered in a 40-day period of the first wave of the pandemic in Denmark,Finland,Iceland,Norway and Sweden.Statistical technique of panel data analysis is used to measure the associations between social distancing and COVID-19 indicators in long-run.Results:Results of dynamic long-run models confirm that a 1%rise in social distancing by reducing human contacts may decline daily deaths,daily infections,all hospital beds needed,beds/nurses needed in ICUs and beds/nurses needed in infection wards due COVID-19 pandemic by 1.13%,15.26%,1.10%,1.17%and 1.89%,respectively.Moreover,results of error correction models verify that if the equilibriums between these series are disrupted by a sudden change in social distancing,the lengths of restoring back to equilibrium are 67,62,40,22 and 49 days for daily deaths,daily infections,all hospital beds needed,nurses/beds needed in ICUs and nurses/beds needed in infection wards,respectively.Conclusion:Proper social distancing was a successful policy for tackling COVID-19 with falling mortality and infection rates as well as the needed hospital resources for patient hospitalizations in Nordic countries.The results alert governments of the need for continuously implementing social distancing policies while using vaccines to prevent national lockdowns and reduce the burden of patient hospitalizations.展开更多
The novel coronavirus responsible for COVID-19 has spread to several countries within a considerably short period.The virus gets deposited in the human nasal cavity and moves to the lungs that might be fatal.As per sa...The novel coronavirus responsible for COVID-19 has spread to several countries within a considerably short period.The virus gets deposited in the human nasal cavity and moves to the lungs that might be fatal.As per safety guidelines by theWorld Health Organization(WHO),social distancing has emerged as one of the major factors to avoid the spread of infection.However,different guidelines are being followed across the countries with regards to what should be the safe distance.Thus,the current work is an attempt to understand the virus deposition pattern in the realistic human nasal cavity and also to find the impact of distance that could be termed as a safety measure.This study is performed usingComputationalFluid Dynamics as a solution tool to investigate the impact of COVID-19 deposition(i)On a realistic 3D human upper airway model and(ii)2D social distancing protocol for a distance of 0.6,1.2,1.8,and 2.4 m.The results revealed that the regional deposition flux within the nasal cavity was predominantly observed in the external nasal cavity and nasopharyngeal section.Frequent flushing of these regions with saltwater substitutes can limit contamination in healthy individuals.The safe distancing limit estimated with 1 m/s airflow was about 1.8 m.The extensive deposition was observed for distances less than 1.8 m in this study,emphasizing the fact that social distancing advisories are not useful and do not take into account the external dynamics associated with airflow.展开更多
The world is experiencing the unprecedented time of a pandemic caused by the coronavirus disease(i.e.,COVID-19).As a countermeasure,contact tracing and social distancing are essential to prevent the transmission of th...The world is experiencing the unprecedented time of a pandemic caused by the coronavirus disease(i.e.,COVID-19).As a countermeasure,contact tracing and social distancing are essential to prevent the transmission of the virus,which can be achieved using indoor location analytics.Based on the indoor location analytics,the human mobility on a site can be monitored and planned to minimize human’s contact and enforce social distancing to contain the transmission of COVID-19.Given the indoor location data,the clustering can be applied to cluster spatial data,spatio-temporal data and movement behavior features for proximity detection or contact tracing applications.More specifically,we propose the Coherent Moving Cluster(CMC)algorithm for contact tracing,the density-based clustering(DBScan)algorithm for identification of hotspots and the trajectory clustering(TRACLUS)algorithm for clustering indoor trajectories.The feature extraction mechanism is then developed to extract useful and valuable features that can assist the proposed system to construct the network of users based on the similarity of the movement behaviors of the users.The network of users is used to model an optimization problem to manage the human mobility on a site.The objective function is formulated to minimize the probability of contact between the users and the optimization problem is solved using the proposed effective scheduling solution based on OR-Tools.The simulation results show that the proposed indoor location analytics system outperforms the existing clustering methods by about 30%in terms of accuracy of clustering trajectories.By adopting this system for human mobility management,the count of close contacts among the users within a confined area can be reduced by 80%in the scenario where all users are allowed to access the site.展开更多
Pandemics have always been a nightmare for humanity,especially in developing countries.Forced lockdowns are considered one of the effective ways to deal with spreading such pandemics.Still,developing countries cannot ...Pandemics have always been a nightmare for humanity,especially in developing countries.Forced lockdowns are considered one of the effective ways to deal with spreading such pandemics.Still,developing countries cannot afford such solutions because these may severely damage the country’s econ-omy.Therefore,this study presents the proactive technological mechanisms for business organizations to run their standard business processes during pandemic-like situations smoothly.The novelty of this study is to provide a state-of-the-art solution to prevent pandemics using industrial internet of things(IIoT)and blockchain-enabled technologies.Compared to existing studies,the immutable and tamper-proof contact tracing and quarantine management solution is proposed.The use of advanced technologies and information security is a critical area for practitioners in the internet of things(IoT)and corresponding solutions.Therefore,this study also emphasizes information security,end-to-end solution,and experimental results.Firstly,a wearable wristband is proposed,incorporating 4G-enabled ultra-wideband(UWB)technology for smart contact tracing mechanisms in industries to comply with standard operating procedures outlined by the world health organization(WHO).Secondly,distributed ledger technology(DLT)omits the centralized dependency for transmitting contact tracing data.Thirdly,a privacy-preserving tracing mechanism is discussed using a public/private key cryptography-based authentication mechanism.Lastly,based on geofencing techniques,blockchain-enabled machine-to-machine(M2M)technology is proposed for quarantine management.The step-by-step methodology and test results are proposed to ensure contact tracing and quarantine management.Unlike existing research studies,the security aspect is also considered in the realm of blockchain.The practical implementation of the proposed solution also obtains the results.The results indicate the successful implementation of blockchain-enabled contact tracing and isolation management using IoT and geo-fencing techniques,which could help battle pandemic situations.Researchers can also consider the 5G-enabled narrowband internet of things(NB-IoT)technologies to implement contact tracing solutions.展开更多
The COVID-19 virus is usually spread by small droplets when talking,coughing and sneezing,so maintaining physical distance between people is necessary to slow the spread of the virus.The World Health Organization(WHO)...The COVID-19 virus is usually spread by small droplets when talking,coughing and sneezing,so maintaining physical distance between people is necessary to slow the spread of the virus.The World Health Organization(WHO)recommends maintaining a social distance of at least six feet.In this paper,we developed a real-time pedestrian social distance risk alert system for COVID-19,whichmonitors the distance between people in real-time via video streaming and provides risk alerts to the person in charge,thus avoiding the problem of too close social distance between pedestrians in public places.We design a lightweight convolutional neural network architecture to detect the distance between people more accurately.In addition,due to the limitation of camera placement,the previous algorithm based on flat view is not applicable to the social distance calculation for cameras,so we designed and developed a perspective conversion module to reduce the image in the video to a bird’s eye view,which can avoid the error caused by the elevation view and thus provide accurate risk indication to the user.We selected images containing only person labels in theCOCO2017 dataset to train our networkmodel.The experimental results show that our network model achieves 82.3%detection accuracy and performs significantly better than other mainstream network architectures in the three metrics of Recall,Precision and mAP,proving the effectiveness of our system and the efficiency of our technology.展开更多
Background: Stigma of mental illness is often examined in social psychology and psychiatric rehabilitation using attitude studies. Participants of these studies are among health professionals and general public member...Background: Stigma of mental illness is often examined in social psychology and psychiatric rehabilitation using attitude studies. Participants of these studies are among health professionals and general public members. A common measure of stigma is using validated scale which measures the opinion on mental illness. Method: A cross-sectional survey was presented to 208 registered nurses. Principal component analyses (with oblique rotation) were used to identify underlying dimensionality in the correlations of items for social distancing. Subscale score variations were analysed across nurse type and ethnicity to examine the discriminant validity of the subscale. Results: Principal component analysis (PCA) revealed one dimension accounting for 43.5% of the variations within items for social distancing. Developed as scale, termed Stigma towards Psychiatric Patients (STPP), reliability analysis indicated high internal consistency with respective alpha coefficient of 0.8. Chinese general nurses scored highest on social distancing than the other three groups: Chinese psychiatric nurses, Anglo general and Anglo psychiatric nurses. Conclusion: Psychometric evaluation of the Stigma Scale (STPP) suggests it is a reliable instrument for measuring social distancing attitudes towards mental illness. The effect of ethnicity on stigmatising attitudes is not entirely accounted for by exposure to people with mental illness.展开更多
This study aims to describe the local wisdom of balala tamakng custom in social distancing during the Covid-19 pandemic.The research approach used was descriptive qualitative with an ethnographic method.The informants...This study aims to describe the local wisdom of balala tamakng custom in social distancing during the Covid-19 pandemic.The research approach used was descriptive qualitative with an ethnographic method.The informants participated were Dayak customary officials.The data collection used was deep interview,and data were validated using sources triangulation,and were analyzed by data reduction,data display,and conclusion drawing.The general conclusion of this research:Balala as a local wisdom in maintaining the balance between humans and the nature that has been passed down from generation to generation is still carried out today.The specific conclusions of this study:(1)Balala is the custom of abstinence in the Kanayatn Dayak community;(2)balala consists of regular balala and balala tamakng;(3)balala tamakng has the meaning as a means of creating a balance between human relations and the universe;(4)there is no direct relationship between the custom of balala tamakng with social and physical distancing against Covid-19.展开更多
Social distancing among people is vital in minimizing spread of COVID-19 within community and can be effective in flattening the outbreak. This research work focuses on developing a close contact proximity detection s...Social distancing among people is vital in minimizing spread of COVID-19 within community and can be effective in flattening the outbreak. This research work focuses on developing a close contact proximity detection system among smartphone users, particularly of COVID-19 patient, using Bluetooth signal to identify and analyze close contact proximity and social distancing from other anonymous smartphone users in their surroundings. Covering a physical space of six feet, a mandatory safety measure in shopping centers, schools, and other crowded areas, is a social solution advocated by World Health Organization (WHO) officials in this COVID-19. Everyone is concerned about their safety in the COVID-19 environment, so we came up with the concept of producing this new equipment. Most of the time, our attention is drawn to those in front of us and to our sides, but we are unable to keep track of those behind us. The major goal of this project is to keep individuals at a safe distance from one another. PIR sensor is used in this proposed work. Why did the World Health Organization (WHO) put 6 feet as a social distancing? When someone coughs or sneezes, small droplets are spread from the cough or sneeze. If you are in close proximity, you can breathe in those droplets, which may contain the COVID-19 virus, according to the World Health Organization. Vanderbilt University infectious disease expert Dr. William Schaffner said the “6 feet distance” rule comes from studies of respiratory physiology. Schaffner explains that even “without a cough or sneeze, the exhaled air mixes with the surrounding air within a distance of 3 to 6 feet, which is known as the breathing zone.” Schaffner continues: “If you are standing 3 to 6 feet away from me, you may inhale droplets that spread through coughing or sneezing. Of course, if I am infected with the virus, these droplets will contain the virus.”展开更多
Social distancing and self-isolation management are crucial preventive measures that can save millions of lives during challenging pandemics of diseases such as the Spanish u,swine u,and coronavirus disease 2019(COVID...Social distancing and self-isolation management are crucial preventive measures that can save millions of lives during challenging pandemics of diseases such as the Spanish u,swine u,and coronavirus disease 2019(COVID-19).This study describes the comprehensive and effective implementation of the Industrial Internet of Things and machine-to-machine technologies for social distancing and smart self-isolation management.These technologies can help prevent outbreaks of any disease that can disperse widely and develop into a pandemic.Initially,a smart wristband is proposed that incorporates Bluetooth beacon technology to facilitate the tracing and tracking of Bluetooth Low Energy beacon packets for smart contact tracing.Second,the connectivity of the device with Android or iOS applications using long-term evolution technology is realized to achieve mobility.Finally,mathematical formulations are proposed to measure the distance between coordinates in order to detect geo-fencing violations.These formulations are specically designed for the virtual circular and polygonal boundaries used to restrict suspected or infected persons from trespassing in predetermined areas,e.g.,at home,in a hospital,or in an isolation ward.The proposed framework outperforms existing solutions,since it is implemented on a wider scale,provides a range of functionalities,and is cost-effective.展开更多
Social distancing during COVID-19 has become one of the most important measures in reducing the risks of the spread of the virus. Implementing thesemeasures at universities is crucial and directly related to the physi...Social distancing during COVID-19 has become one of the most important measures in reducing the risks of the spread of the virus. Implementing thesemeasures at universities is crucial and directly related to the physical attendance ofthe populations of students, professors, employees, and other members on campus. This research proposes an automated scheduling approach that can help universities and schools comply with the social distancing regulations by providingassistance in avoiding huge assemblages of people. Furthermore, this paper proposes a novel course timetable-scheduling scheme based on four main constraints.First, a distance of two meters must be maintained between each student inside theclassroom. Second, no classrooms should contain more than 20% of their regularcapacity. Third, there would be no back-to-back classes. Lastly, no lectures shouldbe held simultaneously in adjacent classrooms. The proposed approach wasimplemented using a variable neighborhood search (VNS) approach with an adaptive neighborhood structure (AD-NS) to resolve the problem of scheduling coursetimetables at Al-Ahlyyia Amman University. However, the experimental resultsshow that the proposed techniques outperformed the standard VNS tested on university course timetabling benchmark dataset ITC2007-Track3. Meanwhile, theapproach was tested using datasets collected from the faculty of information technology at Al-Ahlyyia Amman University (Jordan). Where the results showed that,the proposed technique could help educational institutes to resume their regularoperations while complying with the social distancing guidelines.展开更多
At the beginning of August 2020,the Rio Grande Valley(RGV)of Texas experienced a rapid increase of coronavirus disease 2019(abbreviated as COVID-19)cases and deaths.This study aims to determine the optimal levels of e...At the beginning of August 2020,the Rio Grande Valley(RGV)of Texas experienced a rapid increase of coronavirus disease 2019(abbreviated as COVID-19)cases and deaths.This study aims to determine the optimal levels of effective social distancing and testing to slow the virus spread at the outset of the pandemic.We use an age-stratified eight compartment epidemiological model to depict COVID-19 transmission in the community and within households.With a simulated 120-day outbreak period data we obtain a post 180-days period optimal control strategy solution.Our results show that easing social distancing between adults by the end of the 180-day period requires very strict testing a month later and then daily testing rates of 5%followed by isolation of positive cases.Relaxing social distancing rates in adults from 50%to 25%requires both children and seniors to maintain social distancing rates of 50%for nearly the entire period while maintaining maximum testing rates of children and seniors for 150 of the 180 days considered in this model.Children have higher contact rates which leads to transmission based on our model,emphasizing the need for caution when considering school reopenings.展开更多
This study investigates the role of job characteristics on an individual’s decisions to follow social distancing policies,work,and apply for unemployment insurance in the United States during the COVID-19 pandemic.We...This study investigates the role of job characteristics on an individual’s decisions to follow social distancing policies,work,and apply for unemployment insurance in the United States during the COVID-19 pandemic.We use data that track millions of mobile devices and their daily movements across physical locations to measure whether the devices’owners leave their homes,or work part-time or fulltime on a given day,and we also collect data on weekly unemployment insurance claims.We find that the presence of jobs with a high work-ffom-home capacity in a region increases the ability of people to follow social distancing policies and decreases their unemployment risk,whereas the presence of jobs with high physical proximity decreases the incidences of following social distancing policies and unemployment and increases the incidence of work during the pandemic.These heterogeneous responses based on local job characteristics persist even conditional on a broad set of demographic and socioeconomic variables.展开更多
To enhance the accuracy of path planning of unmanned surface vehicles(USVs),the particle swarm optimization algorithm(PSO)is improved based on species migration strategies observed in ecology.By incorporating the conc...To enhance the accuracy of path planning of unmanned surface vehicles(USVs),the particle swarm optimization algorithm(PSO)is improved based on species migration strategies observed in ecology.By incorporating the concept of particle sight distance,an improved algorithm,called SD-IPSO,is proposed for the real-time autonomous navigation of USVs in marine environments.The algorithm refines the individual behavior pattern of particles in the population,effectively improving both local and global search capabilities while avoiding premature convergence.The effectiveness of the algorithm is validated using standard test functions from CEC-2017 function library,assessing it from multiple dimensions.Sensitivity analysis is conducted on key parameters in the algorithm,including particle sight distance and population size.Results indicate that compared with PSO,SD-IPSO demonstrates significant advantages in optimization accuracy and convergence speed.The application of SD-IPSO in path planning is further investigated through a 14-point traveling salesman problem(TSP)example and navigation autonomous tests of USVs in marine environments.Findings demonstrate that the proposed algorithm exhibits superior optimization capabilities and can effectively address the path planning challenges of USVs.展开更多
Background:In late March 2020,a“Stay Home,Stay Healthy”order was issued in Washington State in response to the COVID-19 pandemic.On May 1,a 4-phase reopening plan began.We investigated whether adjunctive prevention ...Background:In late March 2020,a“Stay Home,Stay Healthy”order was issued in Washington State in response to the COVID-19 pandemic.On May 1,a 4-phase reopening plan began.We investigated whether adjunctive prevention strategies would allow less restrictive physical distancing to avoid second epidemic waves and secure safe school reopening.Methods:We developed a mathematical model,stratifying the population by age,infection status and treatment status to project SARS-CoV-2 transmission during and after the reopening period.The model was parameterized with demographic and contact data from King County,WA and calibrated to confirmed cases,deaths and epidemic peak timing.Adjunctive prevention interventions were simulated assuming different levels of pre-COVID physical interactions(pC_PI)restored.Results:The best model fit estimated~35%pC_PI under the lockdown which prevented~17,000 deaths by May 15.Gradually restoring 75%pC_PI for all age groups between May 15-July 15 would have resulted in~350 daily deaths by early September 2020.Maintaining<45%pC_PI was required with current testing practices to ensure low levels of daily infections and deaths.Increased testing,isolation of symptomatic infections,and contact tracing permitted 60%pC_PI without significant increases in daily deaths before November and allowed opening of schools with<15 daily deaths.Inpatient antiviral treatment was predicted to reduce deaths significantly without lowering cases or hospitalizations.Conclusions:We predict that widespread testing,contact tracing and case isolation would allow relaxation of physical distancing,as well as opening of schools,without a surge in local cases and deaths.展开更多
Physical distancing and contact tracing are two key components in controlling the COVID-19 epidemics.Understanding their interaction at local level is important for policymakers.We propose a flexible modeling framewor...Physical distancing and contact tracing are two key components in controlling the COVID-19 epidemics.Understanding their interaction at local level is important for policymakers.We propose a flexible modeling framework to assess the effect of combining contact tracing with different physical distancing strategies.Using scenario tree analyses,we compute the probability of COVID-19 detection using passive surveillance,with and without contact tracing,in metropolitan Barcelona.The estimates of detection probability and the frequency of daily social contacts are fitted into an age-structured susceptible-exposed-infectious-recovered compartmental model to simulate the epidemics considering different physical distancing scenarios over a period of 26 weeks.With the original Wuhan strain,the probability of detecting an infected individual without implementing physical distancing would have been 0.465,0.515,0.617,and 0.665 in designated age groups(0e14,15e49,50e64,and>65),respectively.As the physical distancing measures were reinforced and the disease circulation decreased,the interaction between the two interventions resulted in a reduction of the detection probabilities;however,despite this reduction,active contact tracing and isolation remained an effective supplement to physical distancing.If we relied solely on passive surveillance for diagnosing COVID-19,the model required a minimal 50%(95%credible interval,39e69%)reduction of daily social contacts to keep the infected population under 5%,as compared to the 36%(95%credible interval,22e56%)reduction with contact tracing systems.The simulation with the B.1.1.7 and B.1.167.2 strains shows similar results.Our simulations showed that a functioning contact tracing program would reduce the need for physical distancing and mitigate the COVID-19 epidemics.展开更多
Despite the geographical distance between China and Africa,the rich customs and lifestyles of the African people present an interesting area of study for international professionals.It is this facet of Africa that fas...Despite the geographical distance between China and Africa,the rich customs and lifestyles of the African people present an interesting area of study for international professionals.It is this facet of Africa that fascinated us most during our research journey across the continent.展开更多
Urban green spaces have positive effects on both physical and mental wellbeing.However,few studies have focused on the trends and thresholds of the effects of different influences on restorative benefits when viewing ...Urban green spaces have positive effects on both physical and mental wellbeing.However,few studies have focused on the trends and thresholds of the effects of different influences on restorative benefits when viewing scenes differfeaturing plant communities.We measured subjective evaluations and objective physiological data from 44 participants who viewed images of plant communities in the yellow to green hue range to compare differences in restorative benefits among plant communities at different visual distances,as well as quantifying the influencing factors involved.The following results were found:(1)Coniferous and multi-layered plant communities were found to provide greater restorative benefits,and the restorative benefits grew with increasing visual distance.(2)Shape and color characteristics were significantly correlated with restorative benefits,but the relationship is not simply linear.(3)The restorative benefits were found to be greatest when crown proportion was 61.23%,trunk proportion ranged from 4.11%to 13.70%,and the value of color index value ranged from 25.44%to 35.56%;the restorative benefits gradually increased when sky proportion exceeded 12.95%-13.19%,the fractal dimension exceeded 1.62-1.67,and hue index exceeded 91.64°-95.67°;additionally,the restorative benefits decreased when the saturation index increased.This study provides a scientific basis for the construction and improvement of plant landscapes in urban green spaces.展开更多
Urbanization destroys wildlife habitats,fragmenting them into small patches with poor connectivity,leading to population declines in species sensitive to such chan ges.Escape is the most common anti-predator strategy ...Urbanization destroys wildlife habitats,fragmenting them into small patches with poor connectivity,leading to population declines in species sensitive to such chan ges.Escape is the most common anti-predator strategy adopted by birds,refuges in habitats reduce or eliminate predation risk.Therefore,creating habitats with suitable refuges for birds has significant implications for their conservation.However,there have been few studies on refuge selection in birds.This study examined the Eurasian Tree Sparrow(Passer montanus)and Oriental Magpie(Pica serica)in urban and rural areas of Chengde City,northern China by measuring their alert distance(AD),flight initiation distance(FID),an d distance fled(DF)and analyzed their refuge selection characteristics after escaping.The FID/AD ratio was employed to assess the behavioral differences of birds in the risk trade-off.The results showed that the FID and FID/AD of both species were lower in urban areas than in rural areas and were negatively correlated with immediate human density.Sparrow FID was significantly affected by group size and landing substrate type.The FID of sparrows was positively correlated with the group size.The sparrows that fled to bushes escaped earlier.In urban and rural areas,sparrows exhibited significantly lower FID,DF,and FID/AD than magpies.The species adopted different refuge selection strategies,with magpies preferentially selecting trees with greater vertical height and sparrows selecting both trees and bushes.Further analysis indicated that the horizontal and vertical distances fled of both species were lower when fleeing to bushes.Urban planning and conservation areas construction should incorporate the ecological needs of local bird species to rationally configure their habitat structure,thereby optimizing the effect of avian conservation.展开更多
In order to address the issue of overly conservative offline reinforcement learning(RL) methods that limit the generalization of policy in the out-of-distribution(OOD) region,this article designs a surrogate target fo...In order to address the issue of overly conservative offline reinforcement learning(RL) methods that limit the generalization of policy in the out-of-distribution(OOD) region,this article designs a surrogate target for OOD value function based on dataset distance and proposes a novel generalized Q-learning mechanism with distance regularization(GQDR).In theory,we not only prove the convergence of GQDR,but also ensure that the difference between the Q-value learned by GQDR and its true value is bounded.Furthermore,an offline generalized actor-critic method with distance regularization(OGACDR) is proposed by combining GQDR with actor-critic learning framework.Two implementations of OGACDR,OGACDR-EXP and OGACDRSQR,are introduced according to exponential(EXP) and opensquare(SQR) distance weight functions,and it has been theoretically proved that OGACDR provides a safe policy improvement.Experimental results on Gym-MuJoCo continuous control tasks show that OGACDR can not only alleviate the overestimation and overconservatism of Q-value function,but also outperform conservative offline RL baselines.展开更多
With the increasing complexity of logistics operations,traditional static vehicle routing models are no longer sufficient.In practice,customer demands often arise dynamically,and multi-depot systems are commonly used ...With the increasing complexity of logistics operations,traditional static vehicle routing models are no longer sufficient.In practice,customer demands often arise dynamically,and multi-depot systems are commonly used to improve efficiency.This paper first introduces a vehicle routing problem with the goal of minimizing operating costs in a multi-depot environment with dynamic demand.New customers appear in the delivery process at any time and are periodically optimized according to time slices.Then,we propose a scheduling system TS-DPU based on an improved ant colony algorithm TS-ACO to solve this problem.The classical ant colony algorithm uses spatial distance to select nodes,while TS-ACO considers the impact of both temporal and spatial distance on node selection.Meanwhile,we adopt Cordeau’s Multi-Depot Vehicle Routing Problem with Time Windows(MDVRPTW)dataset to evaluate the performance of our system.According to the experimental results,TS-ACO,which considers spatial and temporal distance,is more effective than the classical ACO,which only considers spatial distance.展开更多
文摘Objectives:To measure the effect of social distancing on reducing daily deaths,infections and hospital resources needed for coronavirus disease 2019(COVID-19)patients during the first wave of the pandemic in Nordic countries.Methods:The observations of social distancing,daily deaths,infections along with the needed hospital resources for COVID-19 patient hospitalizations including the numbers of all hospital beds,beds needed in ICUs and infection wards,nursing staffs needed in ICUs and infection wards were collected from the Institute for Health Metrics and Evaluation(IHME)by the University of Washington.The observations of social distancing were based on the reduction in human contact relative to background levels for each location quantified by cell phone mobility data collected from IHME.The weighted data per 100,000 population gathered in a 40-day period of the first wave of the pandemic in Denmark,Finland,Iceland,Norway and Sweden.Statistical technique of panel data analysis is used to measure the associations between social distancing and COVID-19 indicators in long-run.Results:Results of dynamic long-run models confirm that a 1%rise in social distancing by reducing human contacts may decline daily deaths,daily infections,all hospital beds needed,beds/nurses needed in ICUs and beds/nurses needed in infection wards due COVID-19 pandemic by 1.13%,15.26%,1.10%,1.17%and 1.89%,respectively.Moreover,results of error correction models verify that if the equilibriums between these series are disrupted by a sudden change in social distancing,the lengths of restoring back to equilibrium are 67,62,40,22 and 49 days for daily deaths,daily infections,all hospital beds needed,nurses/beds needed in ICUs and nurses/beds needed in infection wards,respectively.Conclusion:Proper social distancing was a successful policy for tackling COVID-19 with falling mortality and infection rates as well as the needed hospital resources for patient hospitalizations in Nordic countries.The results alert governments of the need for continuously implementing social distancing policies while using vaccines to prevent national lockdowns and reduce the burden of patient hospitalizations.
基金The authors are thankful to the Institute of Research and Consulting Studies at King Khalid University for supporting this research through Grant No.#34-67-S-2020.
文摘The novel coronavirus responsible for COVID-19 has spread to several countries within a considerably short period.The virus gets deposited in the human nasal cavity and moves to the lungs that might be fatal.As per safety guidelines by theWorld Health Organization(WHO),social distancing has emerged as one of the major factors to avoid the spread of infection.However,different guidelines are being followed across the countries with regards to what should be the safe distance.Thus,the current work is an attempt to understand the virus deposition pattern in the realistic human nasal cavity and also to find the impact of distance that could be termed as a safety measure.This study is performed usingComputationalFluid Dynamics as a solution tool to investigate the impact of COVID-19 deposition(i)On a realistic 3D human upper airway model and(ii)2D social distancing protocol for a distance of 0.6,1.2,1.8,and 2.4 m.The results revealed that the regional deposition flux within the nasal cavity was predominantly observed in the external nasal cavity and nasopharyngeal section.Frequent flushing of these regions with saltwater substitutes can limit contamination in healthy individuals.The safe distancing limit estimated with 1 m/s airflow was about 1.8 m.The extensive deposition was observed for distances less than 1.8 m in this study,emphasizing the fact that social distancing advisories are not useful and do not take into account the external dynamics associated with airflow.
基金This research was funded by Ministry of Education Malaysia,Grant Number FRGS/1/2019/ICT02/MMU/02/1in part by Monash Malaysia,School of Information Technology(SIT)Collaborative Research Seed Grants 2020.
文摘The world is experiencing the unprecedented time of a pandemic caused by the coronavirus disease(i.e.,COVID-19).As a countermeasure,contact tracing and social distancing are essential to prevent the transmission of the virus,which can be achieved using indoor location analytics.Based on the indoor location analytics,the human mobility on a site can be monitored and planned to minimize human’s contact and enforce social distancing to contain the transmission of COVID-19.Given the indoor location data,the clustering can be applied to cluster spatial data,spatio-temporal data and movement behavior features for proximity detection or contact tracing applications.More specifically,we propose the Coherent Moving Cluster(CMC)algorithm for contact tracing,the density-based clustering(DBScan)algorithm for identification of hotspots and the trajectory clustering(TRACLUS)algorithm for clustering indoor trajectories.The feature extraction mechanism is then developed to extract useful and valuable features that can assist the proposed system to construct the network of users based on the similarity of the movement behaviors of the users.The network of users is used to model an optimization problem to manage the human mobility on a site.The objective function is formulated to minimize the probability of contact between the users and the optimization problem is solved using the proposed effective scheduling solution based on OR-Tools.The simulation results show that the proposed indoor location analytics system outperforms the existing clustering methods by about 30%in terms of accuracy of clustering trajectories.By adopting this system for human mobility management,the count of close contacts among the users within a confined area can be reduced by 80%in the scenario where all users are allowed to access the site.
文摘Pandemics have always been a nightmare for humanity,especially in developing countries.Forced lockdowns are considered one of the effective ways to deal with spreading such pandemics.Still,developing countries cannot afford such solutions because these may severely damage the country’s econ-omy.Therefore,this study presents the proactive technological mechanisms for business organizations to run their standard business processes during pandemic-like situations smoothly.The novelty of this study is to provide a state-of-the-art solution to prevent pandemics using industrial internet of things(IIoT)and blockchain-enabled technologies.Compared to existing studies,the immutable and tamper-proof contact tracing and quarantine management solution is proposed.The use of advanced technologies and information security is a critical area for practitioners in the internet of things(IoT)and corresponding solutions.Therefore,this study also emphasizes information security,end-to-end solution,and experimental results.Firstly,a wearable wristband is proposed,incorporating 4G-enabled ultra-wideband(UWB)technology for smart contact tracing mechanisms in industries to comply with standard operating procedures outlined by the world health organization(WHO).Secondly,distributed ledger technology(DLT)omits the centralized dependency for transmitting contact tracing data.Thirdly,a privacy-preserving tracing mechanism is discussed using a public/private key cryptography-based authentication mechanism.Lastly,based on geofencing techniques,blockchain-enabled machine-to-machine(M2M)technology is proposed for quarantine management.The step-by-step methodology and test results are proposed to ensure contact tracing and quarantine management.Unlike existing research studies,the security aspect is also considered in the realm of blockchain.The practical implementation of the proposed solution also obtains the results.The results indicate the successful implementation of blockchain-enabled contact tracing and isolation management using IoT and geo-fencing techniques,which could help battle pandemic situations.Researchers can also consider the 5G-enabled narrowband internet of things(NB-IoT)technologies to implement contact tracing solutions.
基金This research was funded by the Fundamental Research Funds for the Central Universities,3072022TS0605the China University Industry-University-Research Innovation Fund,2021LDA10004.
文摘The COVID-19 virus is usually spread by small droplets when talking,coughing and sneezing,so maintaining physical distance between people is necessary to slow the spread of the virus.The World Health Organization(WHO)recommends maintaining a social distance of at least six feet.In this paper,we developed a real-time pedestrian social distance risk alert system for COVID-19,whichmonitors the distance between people in real-time via video streaming and provides risk alerts to the person in charge,thus avoiding the problem of too close social distance between pedestrians in public places.We design a lightweight convolutional neural network architecture to detect the distance between people more accurately.In addition,due to the limitation of camera placement,the previous algorithm based on flat view is not applicable to the social distance calculation for cameras,so we designed and developed a perspective conversion module to reduce the image in the video to a bird’s eye view,which can avoid the error caused by the elevation view and thus provide accurate risk indication to the user.We selected images containing only person labels in theCOCO2017 dataset to train our networkmodel.The experimental results show that our network model achieves 82.3%detection accuracy and performs significantly better than other mainstream network architectures in the three metrics of Recall,Precision and mAP,proving the effectiveness of our system and the efficiency of our technology.
文摘Background: Stigma of mental illness is often examined in social psychology and psychiatric rehabilitation using attitude studies. Participants of these studies are among health professionals and general public members. A common measure of stigma is using validated scale which measures the opinion on mental illness. Method: A cross-sectional survey was presented to 208 registered nurses. Principal component analyses (with oblique rotation) were used to identify underlying dimensionality in the correlations of items for social distancing. Subscale score variations were analysed across nurse type and ethnicity to examine the discriminant validity of the subscale. Results: Principal component analysis (PCA) revealed one dimension accounting for 43.5% of the variations within items for social distancing. Developed as scale, termed Stigma towards Psychiatric Patients (STPP), reliability analysis indicated high internal consistency with respective alpha coefficient of 0.8. Chinese general nurses scored highest on social distancing than the other three groups: Chinese psychiatric nurses, Anglo general and Anglo psychiatric nurses. Conclusion: Psychometric evaluation of the Stigma Scale (STPP) suggests it is a reliable instrument for measuring social distancing attitudes towards mental illness. The effect of ethnicity on stigmatising attitudes is not entirely accounted for by exposure to people with mental illness.
文摘This study aims to describe the local wisdom of balala tamakng custom in social distancing during the Covid-19 pandemic.The research approach used was descriptive qualitative with an ethnographic method.The informants participated were Dayak customary officials.The data collection used was deep interview,and data were validated using sources triangulation,and were analyzed by data reduction,data display,and conclusion drawing.The general conclusion of this research:Balala as a local wisdom in maintaining the balance between humans and the nature that has been passed down from generation to generation is still carried out today.The specific conclusions of this study:(1)Balala is the custom of abstinence in the Kanayatn Dayak community;(2)balala consists of regular balala and balala tamakng;(3)balala tamakng has the meaning as a means of creating a balance between human relations and the universe;(4)there is no direct relationship between the custom of balala tamakng with social and physical distancing against Covid-19.
文摘Social distancing among people is vital in minimizing spread of COVID-19 within community and can be effective in flattening the outbreak. This research work focuses on developing a close contact proximity detection system among smartphone users, particularly of COVID-19 patient, using Bluetooth signal to identify and analyze close contact proximity and social distancing from other anonymous smartphone users in their surroundings. Covering a physical space of six feet, a mandatory safety measure in shopping centers, schools, and other crowded areas, is a social solution advocated by World Health Organization (WHO) officials in this COVID-19. Everyone is concerned about their safety in the COVID-19 environment, so we came up with the concept of producing this new equipment. Most of the time, our attention is drawn to those in front of us and to our sides, but we are unable to keep track of those behind us. The major goal of this project is to keep individuals at a safe distance from one another. PIR sensor is used in this proposed work. Why did the World Health Organization (WHO) put 6 feet as a social distancing? When someone coughs or sneezes, small droplets are spread from the cough or sneeze. If you are in close proximity, you can breathe in those droplets, which may contain the COVID-19 virus, according to the World Health Organization. Vanderbilt University infectious disease expert Dr. William Schaffner said the “6 feet distance” rule comes from studies of respiratory physiology. Schaffner explains that even “without a cough or sneeze, the exhaled air mixes with the surrounding air within a distance of 3 to 6 feet, which is known as the breathing zone.” Schaffner continues: “If you are standing 3 to 6 feet away from me, you may inhale droplets that spread through coughing or sneezing. Of course, if I am infected with the virus, these droplets will contain the virus.”
基金supported by Data and Articial Intelligence Scientic Chair at Umm Al-Qura University,Makkah City,Saudi Arabia。
文摘Social distancing and self-isolation management are crucial preventive measures that can save millions of lives during challenging pandemics of diseases such as the Spanish u,swine u,and coronavirus disease 2019(COVID-19).This study describes the comprehensive and effective implementation of the Industrial Internet of Things and machine-to-machine technologies for social distancing and smart self-isolation management.These technologies can help prevent outbreaks of any disease that can disperse widely and develop into a pandemic.Initially,a smart wristband is proposed that incorporates Bluetooth beacon technology to facilitate the tracing and tracking of Bluetooth Low Energy beacon packets for smart contact tracing.Second,the connectivity of the device with Android or iOS applications using long-term evolution technology is realized to achieve mobility.Finally,mathematical formulations are proposed to measure the distance between coordinates in order to detect geo-fencing violations.These formulations are specically designed for the virtual circular and polygonal boundaries used to restrict suspected or infected persons from trespassing in predetermined areas,e.g.,at home,in a hospital,or in an isolation ward.The proposed framework outperforms existing solutions,since it is implemented on a wider scale,provides a range of functionalities,and is cost-effective.
文摘Social distancing during COVID-19 has become one of the most important measures in reducing the risks of the spread of the virus. Implementing thesemeasures at universities is crucial and directly related to the physical attendance ofthe populations of students, professors, employees, and other members on campus. This research proposes an automated scheduling approach that can help universities and schools comply with the social distancing regulations by providingassistance in avoiding huge assemblages of people. Furthermore, this paper proposes a novel course timetable-scheduling scheme based on four main constraints.First, a distance of two meters must be maintained between each student inside theclassroom. Second, no classrooms should contain more than 20% of their regularcapacity. Third, there would be no back-to-back classes. Lastly, no lectures shouldbe held simultaneously in adjacent classrooms. The proposed approach wasimplemented using a variable neighborhood search (VNS) approach with an adaptive neighborhood structure (AD-NS) to resolve the problem of scheduling coursetimetables at Al-Ahlyyia Amman University. However, the experimental resultsshow that the proposed techniques outperformed the standard VNS tested on university course timetabling benchmark dataset ITC2007-Track3. Meanwhile, theapproach was tested using datasets collected from the faculty of information technology at Al-Ahlyyia Amman University (Jordan). Where the results showed that,the proposed technique could help educational institutes to resume their regularoperations while complying with the social distancing guidelines.
文摘At the beginning of August 2020,the Rio Grande Valley(RGV)of Texas experienced a rapid increase of coronavirus disease 2019(abbreviated as COVID-19)cases and deaths.This study aims to determine the optimal levels of effective social distancing and testing to slow the virus spread at the outset of the pandemic.We use an age-stratified eight compartment epidemiological model to depict COVID-19 transmission in the community and within households.With a simulated 120-day outbreak period data we obtain a post 180-days period optimal control strategy solution.Our results show that easing social distancing between adults by the end of the 180-day period requires very strict testing a month later and then daily testing rates of 5%followed by isolation of positive cases.Relaxing social distancing rates in adults from 50%to 25%requires both children and seniors to maintain social distancing rates of 50%for nearly the entire period while maintaining maximum testing rates of children and seniors for 150 of the 180 days considered in this model.Children have higher contact rates which leads to transmission based on our model,emphasizing the need for caution when considering school reopenings.
文摘This study investigates the role of job characteristics on an individual’s decisions to follow social distancing policies,work,and apply for unemployment insurance in the United States during the COVID-19 pandemic.We use data that track millions of mobile devices and their daily movements across physical locations to measure whether the devices’owners leave their homes,or work part-time or fulltime on a given day,and we also collect data on weekly unemployment insurance claims.We find that the presence of jobs with a high work-ffom-home capacity in a region increases the ability of people to follow social distancing policies and decreases their unemployment risk,whereas the presence of jobs with high physical proximity decreases the incidences of following social distancing policies and unemployment and increases the incidence of work during the pandemic.These heterogeneous responses based on local job characteristics persist even conditional on a broad set of demographic and socioeconomic variables.
文摘To enhance the accuracy of path planning of unmanned surface vehicles(USVs),the particle swarm optimization algorithm(PSO)is improved based on species migration strategies observed in ecology.By incorporating the concept of particle sight distance,an improved algorithm,called SD-IPSO,is proposed for the real-time autonomous navigation of USVs in marine environments.The algorithm refines the individual behavior pattern of particles in the population,effectively improving both local and global search capabilities while avoiding premature convergence.The effectiveness of the algorithm is validated using standard test functions from CEC-2017 function library,assessing it from multiple dimensions.Sensitivity analysis is conducted on key parameters in the algorithm,including particle sight distance and population size.Results indicate that compared with PSO,SD-IPSO demonstrates significant advantages in optimization accuracy and convergence speed.The application of SD-IPSO in path planning is further investigated through a 14-point traveling salesman problem(TSP)example and navigation autonomous tests of USVs in marine environments.Findings demonstrate that the proposed algorithm exhibits superior optimization capabilities and can effectively address the path planning challenges of USVs.
基金This work was partially supported by National Institutes of Health(5R01AI121129-05)Centers for Disease Control and Prevention(NU38OT000297-02)Washington Research Foundation.
文摘Background:In late March 2020,a“Stay Home,Stay Healthy”order was issued in Washington State in response to the COVID-19 pandemic.On May 1,a 4-phase reopening plan began.We investigated whether adjunctive prevention strategies would allow less restrictive physical distancing to avoid second epidemic waves and secure safe school reopening.Methods:We developed a mathematical model,stratifying the population by age,infection status and treatment status to project SARS-CoV-2 transmission during and after the reopening period.The model was parameterized with demographic and contact data from King County,WA and calibrated to confirmed cases,deaths and epidemic peak timing.Adjunctive prevention interventions were simulated assuming different levels of pre-COVID physical interactions(pC_PI)restored.Results:The best model fit estimated~35%pC_PI under the lockdown which prevented~17,000 deaths by May 15.Gradually restoring 75%pC_PI for all age groups between May 15-July 15 would have resulted in~350 daily deaths by early September 2020.Maintaining<45%pC_PI was required with current testing practices to ensure low levels of daily infections and deaths.Increased testing,isolation of symptomatic infections,and contact tracing permitted 60%pC_PI without significant increases in daily deaths before November and allowed opening of schools with<15 daily deaths.Inpatient antiviral treatment was predicted to reduce deaths significantly without lowering cases or hospitalizations.Conclusions:We predict that widespread testing,contact tracing and case isolation would allow relaxation of physical distancing,as well as opening of schools,without a surge in local cases and deaths.
基金F.B.and J.R.B.P.acknowledge funding from the European Commission,under Grants 874735(VEO),853271(H-MIP),2020/2094(NextGenerationEU,through CSIC's Global Health Platform,PTI Salud Global).
文摘Physical distancing and contact tracing are two key components in controlling the COVID-19 epidemics.Understanding their interaction at local level is important for policymakers.We propose a flexible modeling framework to assess the effect of combining contact tracing with different physical distancing strategies.Using scenario tree analyses,we compute the probability of COVID-19 detection using passive surveillance,with and without contact tracing,in metropolitan Barcelona.The estimates of detection probability and the frequency of daily social contacts are fitted into an age-structured susceptible-exposed-infectious-recovered compartmental model to simulate the epidemics considering different physical distancing scenarios over a period of 26 weeks.With the original Wuhan strain,the probability of detecting an infected individual without implementing physical distancing would have been 0.465,0.515,0.617,and 0.665 in designated age groups(0e14,15e49,50e64,and>65),respectively.As the physical distancing measures were reinforced and the disease circulation decreased,the interaction between the two interventions resulted in a reduction of the detection probabilities;however,despite this reduction,active contact tracing and isolation remained an effective supplement to physical distancing.If we relied solely on passive surveillance for diagnosing COVID-19,the model required a minimal 50%(95%credible interval,39e69%)reduction of daily social contacts to keep the infected population under 5%,as compared to the 36%(95%credible interval,22e56%)reduction with contact tracing systems.The simulation with the B.1.1.7 and B.1.167.2 strains shows similar results.Our simulations showed that a functioning contact tracing program would reduce the need for physical distancing and mitigate the COVID-19 epidemics.
文摘Despite the geographical distance between China and Africa,the rich customs and lifestyles of the African people present an interesting area of study for international professionals.It is this facet of Africa that fascinated us most during our research journey across the continent.
基金funded by the National Natural Science Foundation of China(32471953)the Educational Department of Liaoning Province Key Research Project(LJ212410153073).
文摘Urban green spaces have positive effects on both physical and mental wellbeing.However,few studies have focused on the trends and thresholds of the effects of different influences on restorative benefits when viewing scenes differfeaturing plant communities.We measured subjective evaluations and objective physiological data from 44 participants who viewed images of plant communities in the yellow to green hue range to compare differences in restorative benefits among plant communities at different visual distances,as well as quantifying the influencing factors involved.The following results were found:(1)Coniferous and multi-layered plant communities were found to provide greater restorative benefits,and the restorative benefits grew with increasing visual distance.(2)Shape and color characteristics were significantly correlated with restorative benefits,but the relationship is not simply linear.(3)The restorative benefits were found to be greatest when crown proportion was 61.23%,trunk proportion ranged from 4.11%to 13.70%,and the value of color index value ranged from 25.44%to 35.56%;the restorative benefits gradually increased when sky proportion exceeded 12.95%-13.19%,the fractal dimension exceeded 1.62-1.67,and hue index exceeded 91.64°-95.67°;additionally,the restorative benefits decreased when the saturation index increased.This study provides a scientific basis for the construction and improvement of plant landscapes in urban green spaces.
基金funded by the Natural Science Foundation of Hebei Province(C2025201032 to J.W.)High-Level Talents Research Start-Up Project of Hebei University(521100222044 to J.W.)+1 种基金the Huizhi Lead Innovation Space Project in High-tech Zone of Chengde City(HZLC202410 to L.M.)National Undergraduate Innovation and Entrepreneurship Training Program(202510098011 to H.Z.)。
文摘Urbanization destroys wildlife habitats,fragmenting them into small patches with poor connectivity,leading to population declines in species sensitive to such chan ges.Escape is the most common anti-predator strategy adopted by birds,refuges in habitats reduce or eliminate predation risk.Therefore,creating habitats with suitable refuges for birds has significant implications for their conservation.However,there have been few studies on refuge selection in birds.This study examined the Eurasian Tree Sparrow(Passer montanus)and Oriental Magpie(Pica serica)in urban and rural areas of Chengde City,northern China by measuring their alert distance(AD),flight initiation distance(FID),an d distance fled(DF)and analyzed their refuge selection characteristics after escaping.The FID/AD ratio was employed to assess the behavioral differences of birds in the risk trade-off.The results showed that the FID and FID/AD of both species were lower in urban areas than in rural areas and were negatively correlated with immediate human density.Sparrow FID was significantly affected by group size and landing substrate type.The FID of sparrows was positively correlated with the group size.The sparrows that fled to bushes escaped earlier.In urban and rural areas,sparrows exhibited significantly lower FID,DF,and FID/AD than magpies.The species adopted different refuge selection strategies,with magpies preferentially selecting trees with greater vertical height and sparrows selecting both trees and bushes.Further analysis indicated that the horizontal and vertical distances fled of both species were lower when fleeing to bushes.Urban planning and conservation areas construction should incorporate the ecological needs of local bird species to rationally configure their habitat structure,thereby optimizing the effect of avian conservation.
基金supported by the National Natural Science Foundation of China(62373364,62176259)the Key Research and Development Program of Jiangsu Province(BE2022095)。
文摘In order to address the issue of overly conservative offline reinforcement learning(RL) methods that limit the generalization of policy in the out-of-distribution(OOD) region,this article designs a surrogate target for OOD value function based on dataset distance and proposes a novel generalized Q-learning mechanism with distance regularization(GQDR).In theory,we not only prove the convergence of GQDR,but also ensure that the difference between the Q-value learned by GQDR and its true value is bounded.Furthermore,an offline generalized actor-critic method with distance regularization(OGACDR) is proposed by combining GQDR with actor-critic learning framework.Two implementations of OGACDR,OGACDR-EXP and OGACDRSQR,are introduced according to exponential(EXP) and opensquare(SQR) distance weight functions,and it has been theoretically proved that OGACDR provides a safe policy improvement.Experimental results on Gym-MuJoCo continuous control tasks show that OGACDR can not only alleviate the overestimation and overconservatism of Q-value function,but also outperform conservative offline RL baselines.
基金supported by the Startup Foundation for Introducing Talent of Nanjing University of Information Science and Technology.
文摘With the increasing complexity of logistics operations,traditional static vehicle routing models are no longer sufficient.In practice,customer demands often arise dynamically,and multi-depot systems are commonly used to improve efficiency.This paper first introduces a vehicle routing problem with the goal of minimizing operating costs in a multi-depot environment with dynamic demand.New customers appear in the delivery process at any time and are periodically optimized according to time slices.Then,we propose a scheduling system TS-DPU based on an improved ant colony algorithm TS-ACO to solve this problem.The classical ant colony algorithm uses spatial distance to select nodes,while TS-ACO considers the impact of both temporal and spatial distance on node selection.Meanwhile,we adopt Cordeau’s Multi-Depot Vehicle Routing Problem with Time Windows(MDVRPTW)dataset to evaluate the performance of our system.According to the experimental results,TS-ACO,which considers spatial and temporal distance,is more effective than the classical ACO,which only considers spatial distance.
